1. Field of the Invention
The present relates, in general, to an automatic door operating system, and more particularly to an automatic slide door operating system for use in a motor vehicle. More specifically, the present invention is concerned with an automatic slide door operating system in which the opening and closing movement of the door is carried out by a power device, upon manipulation of a control switch.
2. Description of the Prior Art
Hitherto, in motor vehicles, particularly, in so-called "one-box" type motor vehicles having slide doors, various power systems have been proposed and put into practical use for opening and closing the door with an aid of a power device. Some of them are described in Japanese Patent First Provisional Publications Nos. 58-178778 and 1-164647.
The systems disclosed by these publications are of a type which generally comprises a door moving device which is mounted to a vehicle body for moving the slide door in both directions to open and close a door opening of the vehicle, a door closing device which is mounted in the door for enforcedly shifting the door from a half-latch position to a full-close latched position relative to the door opening, and a latch cancelling device for canceling the latched condition of the door just before starting of the door opening operation of the door moving device.
Both the door moving device and the door closing device use electric motors as a prime mover.
The reason for the door closing device in addition to the door moving device is that the shifting of the door from the half-latch position to the full-close latched position needs a great force because of a considerable resistance offered by an elastomeric door seal fixed to the door. In fact, the door shifting from the half-latch position to the full-close latched position is not achieved by only the door moving device.
That is, when the door is slid to the half-latch position by the door moving device, the door closing device starts to operate for shifting the door from the half-latch position to the full-close latched position in cooperation with the door moving device.
For allowing the door closing device to produce a higher torque needed for the door shifting from the half-latch position to the full-close latched position, the door closing device is equipped with a speed reduction gear by which the output speed of the associated electric motor is very much lowered.
However, these conventional door operating systems have several drawbacks caused by the provision of two power devices, i.e., the door moving device and the door closing device.
One of the drawbacks is that, under the shifting of the door from the half-latch position to the full-close latched position, the door shifting speed offered by the door closing device is very much lower than that provided by the door moving device because of the large speed reduction made by the speed reduction gear of the door closing device. This phenomenon brings about an overload of both power devices thereby shortening their lives.